Terror probers reported two big breaks in the al Qaeda manhunt yesterday – the arrest in Pakistan of a mastermind of the Sept. 11 attacks, and the capture of a suspected five-man al Qaeda cell near Buffalo.

U.S. investigators are looking into possible ties between Ramzi Binalshibh, who was captured during a bloody gun battle in Karachi, Pakistan, and the five upstate men, who like Binalshibh are of Yemeni descent.

Binalshibh, 30, is the former roommate of Mohamed Atta, the ringleader of the 9/11 hijackers. He is believed to have been closely involved from the start in the planning of the World Trade Center and Pentagon attacks.

He even tried to enter the United States five times before Sept. 11 – and is believed to have been designated as the 20th hijacker – but was denied a visa, investigators said.

Sources told The Post the men – four of whom appear to be native-born Americans – were arrested on terror-related charges, but documents concerning them have been sealed.

The Yemeni men, who lived a block from one another and attended the same mosque, were picked up because of a recent increase in communications with suspected terrorists overseas, U.S. officials said.

Officials said the discovery of the cell and the surge in overseas contacts was one reason President Bush raised the United States to an “orange” alert, the second-highest level, earlier this week.

But they said there was no evidence the men were preparing any terrorist attacks.

Albaneh Mosed, a relative of one suspect, said the men weren’t terrorists. “I would put my life on the line just to prove they’re innocent,” Mosed said.

Information from suspects recently questioned overseas led investigators to the Buffalo cell, to another uncovered in Detroit last month and to at least one cell on the West Coast, sources told The Post.

The Buffalo cell had been under surveillance for several weeks, sources said.

He was captured in a raid on a Karachi safe house on Wednesday, the attacks’ anniversary.

Pakistani police – aided by information from the CIA and FBI – believed they were hot on the trail of another top-ranking al Qaeda fugitive, Khalid Sheik Mohammed, when they seized Binalshibh and four other al Qaeda men in Karachi.

Initial reports said Binalshibh was flown to Germany by American authorities. But later reports said it was unclear where he was being held.

The Times of London quoted Pakistani officials as saying Mohammed, who has a $20 million bounty on his head and has been indicted in New York, was one of nine suspects seized in raids in Karachi – but U.S. sources disputed that.

Police were seeking Mohammed in Wednesday’s Karachi raid – which set off a four-hour gun battle.

Two al Qaeda fighters were killed in the fight. One wrote “God is great” in his own blood before dying.

Seven police officers were wounded and Binalshibh was among five suspected terrorists captured, authorities said.

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BEHIND THE SLIMES: PROFILES IN MASS MURDER

KHALID SHEIK MOHAMMED

* Born in Pakistan in 1964

* Uncle of Ramzi Yousef, who was found guilty of plotting the 1993 attack on the World Trade Center.

* Briefed Mohammed Atta on the Sept. 11 attacks in his role as al Qaeda’s military specialist.

* On the FBI’s Most Wanted List for masterminding attack on the USS Cole in October 2000 and indicted in New York in 1995 for plotting to bomb 12 airliners.

* Still at large.

RAMZI BINALSHIBH

* Born in Yemen in 1972.

* Sept. 11 ringleader Mohammed Atta’s roommate in Hamburg.

* Believed to have originally been designated as the 20th hijacker, but was denied a U.S. visa several times.

* Made money transfers and helped plan logistical details of the Sept. 11 attacks, but fled to Pakistan shortly before the hijackings.